Cyclone furnaces



May 26, 1959 E. HUBEL CYCLONE FURNACES 2 Sheets-Sheet 2 Filed April 2. 1956 INVENTOR.

Ernsi' Hiibel ATTORNEY United States Patent CYCLONE FURNACES Ernst Hubel, Oberhausen, Germany, assignor to The Babcock 8: Wilcox Company, New York, N.Y., a corporation of New Jersey Application April 2, 1956, Serial No. 575,489

6 Claims. Cl. 122-240 This invention relates in general to a fluid heating unit and more particularly to a fluid heating unit adapted to be fired by one or more furnaces of circular cross-section each having a concentric gas outlet at one end and designed for the burning of a particle-form slag-forming solid fuel, such furnaces being known in the art as cyclone furnaces. Furnaces of this general type are described in U.S. Patent No. 2,594,312.

Heretofore, it has been customary to position the cyclone furnace laterally adjacent and opening to a vertically elongated chamber, with the major axis of the cyclone furnace arranged substantially horizontal, the high temperature gases discharging from the cyclone furnace through a re-entrant throat positioned in a vertical wall of said chamber, and the entire axial length of the cyclone furnace disposed outside of said chamber. While satisfactory operation has been obtained with the cyclone furnace so arranged, some difl'lculty has been encountered in providing for effective fluid circulation in the tubes defining the cyclone furnace walls. It is also customary to operate cyclone furnaces under substantial internal pressure and should a hole develop in the refractory material covering the wall tubes defining the cyclone furnace flames and molten slag would discharge to the atmosphere, thus necessitating immediate shutdown of the unit.

The present invention is concerned with the provision of an improved construction of a fluid heating unit comprising upwardly extending walls including fluid cooled tubes defining a secondary furnace chamber receiving the products of combustion directly from a cyclone type furnace, the axis of which is preferably arranged substantially horizontal and the axial length of which is disposed in most part within the secondary furnace chamber, with some of the fluid cooled tubes of the secondary furnace chamber having intermediate portions forming the combustion chamber of the cyclone furnace. With this arrangement the wall tubes forming the combustion chamber of the cyclone furnace are exposed to the heat of the gases on one side along a substantial portion of their length, while a portion of said tubes are subject to the heat of the gases on both sides, thus promoting continuous and effective circulation in these wall tubes. This arrangement also provides a more compact installation than heretofore known. Moreover, in the event that an opening develops in the refractory material covering the wall tubes partitioning the cyclone furnace from the secondary furnace chamber operation is unlikely to be seriously affected since flame penetration and slag discharge would be directed to the secondary furnace chamber.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, refer- 2,887,992 Patented May 26, 1959 descriptive matter in which I have illustrated and described a preferred embodiment of my invention.

Of the drawings:

Fig. l is a sectional side elevation of a cyclone furnace fired fluid heating unit constructed in accordance with my invention, the section being taken along the line 11 of Fig. 2;

Fig. 2 is a sectional rear elevation taken along the line 2-2 of Fig. 1; and

Fig. 3 is a sectional rear elevation of another form of cyclone furnace fired fluid heating unit constructed in accordance with my invention.

While various kinds of liquid and gas fuels can be burned in the cyclone furnace construction illustrated, the constructions illustrated and hereinafter described are specifically designed and particularly adapted for burning coarsely pulverized or granulated bituminous or semibituminous coal; and although the invention is illustrated as embodied in a natural circulation fluid heating unit, the invention in its broader aspects may be carried out in a forced flow fluid heating unit.

The main portions of the unit illustrated include a fuel fin'ng section consisting of a plurality of independently operable cyclone furnaces 10 of relatively small volume and boundary wall area arranged to burn a solid fuel at high rates of heat release and separately discharging high temperature gaseous products of combustion and separated ash residue as a molten slag into a secondary furnace chamber 12 formed in the lower portion of the fluid heating unit The heating gases with a small amount of molten ash in suspension are directed downwardly within the chamber 12 and then pass upwardly ence should be had to the accompanying drawings and between the cyclone furnaces 10. The gases then flow through a slag collecting screen 14 into a vertically elongated radiant heat transfer chamber 16 of rectangular horizontal cross-section, and thence to a convection heating section, not shown.

The secondary furnace chamber 12 is of rectangular horizontal cross-section, being defined by a water-cooled front or target wall 18, rear wall 20, opposite side walls 22, and roof 24, and partitioned from the cyclone furnaces 10 by portions of the circumferential wall of each cyclone furnace combustion chamber. The secondary furnace chamber 12 opens upwardly into the radiant chamber 16, which is formed by vertical extensions of the roof, side, and rear boundaries of the chamber 12. The lower end of the secondary furnace chamber 12 is suitably formed as a hopper having inclined side wall portions 24 and front wall portions 26 converging downwardly toward a rectangular throat passage 28 for discharging molten slag into a slag tank 30 positioned therebelow. A mechanical conveyor 32 conveys the cooled slag and ash from the slag tank.

The cyclone furnaces 10 are mounted at a common elevation in the rear wall 20 and are arranged symmetrically about a vertical axis of the chamber 12. Each cyclone furnace comprises an elongated combustion chamber 34 of substantially circular cross-section arranged with its major axis substantially horizontal and having the major portion of its axial length disposed within the chamber 12. The topmost portion of each combustion chamber lies in substantially the same plane as the plane of the roof 24, and the major axis of each lies in approximately the same plane as the plane of its associated side wall 22. Each combustion chamber 34 is formed by closely spaced studded tubes covered by a layer of refractory material. The outer end of each chamber 34 is formed with an inwardly flaring frusto-conical wall 36 extending outwardly from the plane of the rear wall 20. The inner end of each chamber 34 has a fluid cooled wall including an inwardly projecting throat 38 forming a gas outlet 40 flaring towards its discharge end. A circular port 42 arranged on the outer end of the frustoconical wall 36 is provided with a door 44 for inspection and access. The frusto-conical wall 36 and the port 42 are covered with insulation 46 and casing 43. Coarsely pulverized or granulated bituminous or semi-bituminous coal carried in a stream of preheated primary air is introduced tangentially through fuel inlets 52 along the portion of the length of each combustion chamber superjacent the outlet throat 33. Streams of secondary air are admitted tangentially through secondary air ports 54 in the same direction of rotation and at the outer side of the streams of fuel laden air discharging from the fuel inlets 52. An opening 56 is provided in the lower rear portion of each combustion chamber for the continuous discharge of molten slag resulting from combustion of ash-containing fuel.

All boundaries of the secondary furnace and radiant chambers 12 and 16 are fluid cooled by means of fluid conducting tubes associated with the respective walls, the tube portions in the secondary furnace chamber being studded and covered with refractory material and those in the radiant chamber being bare. The front wall 18 of the secondary furnace chamber 12 and of the radiant chamber 16, as well as the roof 2 and the hopper 26, are lined by tubes 58 having their lower ends connected to a header 60. Some of these tubes serve to form the slag screen 14 arranged across the outlet from the secondary furnace chamber 12. The rear wall 2! of the secondary furnace and radiant chambers 12 and 16 are lined by tubes 62 having their lower ends connected to a header 6%. Some of the tubes 62 have intermediate portions 62A which form the frusto-conical Wall 36 of each combustion chamber. Each side wall 22 is cooled by a row of tubes 66, some of which line the secondary furnace chamber 12 forwardly of the gas outlet 40 and have their lower ends connected to a header 68 and their upper ends to a header 70. The remainder of the tubes 66 line the remainder of the side Wall portions of the secondary furnace chamber 12 and the side Walls of the radiant chamber 16 and have their lower ends connected to the header 68. Intermediate tube portions 66A and 66B of these latter tubes 66 form the cylindrical wall and inner end wall, respectively, of each combustion chamber. It is to be understood that the portions of the fluid circulation system described are suitably connected into the natural circulation system of the unit. For example, the upper ends of tube rows 58 and 62 may be connected to a steam and water drum and the headers 60 and 64 may be supplied with water from the water space of said drum.

The gases discharging from each cyclone furnace throat 38 contain little, if any, combustible matter, combustion being substantially completed in the furnace. A small amount of fly ash and molten particles is present in suspension in the outgoing gases, and this residue is largely removed in the secondary furnace chamber 12. Molten slag resulting from combustion continuously discharges through the opening 56 of each cyclone furnace and flows down the side and hopper walls 22 and 24 into the slag tank 30, along with ash and slag particles which may be separated in the secondary furnace chamber 12. The products of combustion from each cyclone furnace discharge at high velocity into the secondary furnace chamber 12 and due to the proximity of the front or target wall 18, which is preferably spaced horizontally from the gas outlet 40 a distance not greater than the diameter of the cyclone furnace, the gas stream impacts on the front wall and is forced to move downwardly by the enclosing roof 24. The adhesive property of the slag particles and this relatively abrupt change in the movement of the gas stream results in most of the remaining ash and slag particles in suspension being deposited on the front wall 18 and from there drained downwardly along the hopper wall 26 to the slag tank 30.

After making the downward turn at the front wall the gases flow rearwardly and then upwardly between the cyclone furnaces to the slag collecting screen 14. Thus a substantial portion of the circumferential wall of each combustion chamber is exposed to the heat of the gases on both of its sides, thereby enhancing the circulation of the cooling fluid through these tubes.

Fig. 3 illustrates a natural circulation fluid heating unit modified for firing by a plurality of cyclone furnaces 72 of the general construction illustrated in Figs. 1 and 2, in each of which the circumferential wall of the combustion chamber serves as a partition between the cyclone furnace and the secondary furnace chamber. As in Figs. 1 and 2, the cyclone furnaces are mounted at a common elevation in the rear wall, each having walls including fluid cooled tubes defining a combustion chamber of substantially circular cross-section arranged with its major axis substantially horizontal and having the major portion of its axial length disposed within the secondary furnace chamber, and the relation of the cyclone furnaces with respect to the secondary furnace and radiant chambers is generally the same. In this modification, the entire circumferential wall of each combustion chamber, as well as a substantial portion of the tube lengths leading thereto and therefrom are exposed to the heat of the gases on both sides to further promote circulation in these tubes. The supply tubes to the central combustion chamber are studded and refractory covered to form an imperforate wall 74, the lower portions of these tubes being alternately oppositely inclined to line hopper surfaces 76 and 78 and having their lower ends respectively connected to headers 80 and 82. The supply tubes of the other combustion chambers extend as groups of spaced tubes 84 and 86 having their lower ends respectively connected to headers 88 and 90 which also serve to supply the fluid conducting tubes lining the side walls of the secondary furnace and radiant chambers. The tubes leading from each combustion chamber are studded and refractory covered to form imperforate walls 92, 94, and 96. Alternatively, these tubes may be arranged to form a slag screen.

While in accordance with the provisions of the statutes I have illustrated and described herein a specific form of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

l. A fluid heating unit having a fluid circulation system and comprising upwardly extending walls including upwardly extending fluid cooled tubes defining a secondary furnace chamber, circumferential and end walls including intermediate portions of some of the fluid cooled tubes of said secondary furnace chamber Walls defining la combustion chamber of substantially circular cross-section arranged with its axis substantially horizontal and having the major portion of its axial length extending into said secondary furnace chamber, with substantially the entire length of at least a portion of said circumferential wall being formed by one of the outer boundary walls of said secondary furnace chamber, means forming a gas outlet in one of said end walls of said combustion chamber opening to said secondary furnace chamber, means including combustion chamber fuel and air inlets disposed exteriorly of said secondary furnace chamber for introducing a combustible mixture into said combustion chamber for discharge through said gas outlet into said secondary furnace chamber, said secondary furnace chamber including an upwardly extending wall disposed opposite and close to said gas outlet and arranged to direct the gases discharging from said combustion chamber over and into heat transfer relation with a portion of the outer surface of the circumferential wall of said combustion chamber,

whereby a part of thefluid cooled tubes of said combustion chamber absorb heat concurrently from the hot gases therein and from the gases flowing through said secondary furnace chamber, and means connecting said fluid cooled tubes into said fluid circulation system.

2 A fluid heating unit having a fluid circulation system and comprising upwardly extending walls including upwardly extending fluid cooled tubes defining a secondary furnace chamber, a circumferential wall defining in part a combustion chamber of substantially circular cross-section having the major portion of its axial length extending intosaid secondary furnace chamber, with substantially the entire length of at least a portion of said circumferential wall being formed by an intermediate portion of one of the outer boundary walls of said secondary furnace chamber and a portion of some of the fluid cooled tubes thereof, means forming a gas outlet in an end wall of said combustion chamber opening to said secondary furnace chamber, means including combustion chamber fuel and air inlets disposed exteriorly of said secondary furnace chamber for introducing a combustible mixture into said combustion chamber for discharge through said gas outlet into said secondary furnace chamber, said secondary furnace chamber including an upwardly extending wall disposed opposite and close to said gas outlet and arranged to direct the gases discharging from said combustion chamber over and into heat transfer relation with a portion of the outer surface of the circumferential wall of said combustion chamber, whereby a part of the fluid cooled tubes of said circumferential wall absorb heat concurrently from the hot gases therein and from the gases flowing through said secondary furnace chamber, and means connecting said fluid cooled tubes into said fluid circulation system.

3. A fluid heating unit having a fluid circulation system and comprising upwardly extending walls including upwardly extending fluid cooled tubes defining a secondary furnace chamber, a plurality of cyclone furnaces each having a substantially cylindrical combustion chamber arranged with its axis substantially horizontal and defined by circumferential and end walls including intermediate portions of some of the fluid cooled tubes of said sec ondary furnace chamber walls, each combustion chamber having the major portion of its axial length extending into said secondary furnace chamber, with substantially the entire length of at least a portion of the circumferential wall of each combustion chamber being formed by one of the outer boundary walls of said secondary furnace chamber, a gas outlet in one of said end walls of each combustion chamber opening to said secondary furnace chamber, means including combustion chamber fuel and air inlets disposed exteriorly of said secondary furnace chamber for introducing a combustible mixture into each combustion chamber for discharge through its respective gas outlet into said secondary furnace chamber, said secondary furnace chamber including an upwardly extending wall disposed opposite and close to said gas outlets and arranged to direct the gases discharging from each combustion chamber over and into heat transfer relation with a portion of the outer surface of the circumferential wall of each combustion chamber, whereby a part of the fluid cooled tubes of each combustion chamber absorb heat concurrently from the hot gases therein and from the gases flowing through said secondary furnace chamber, and means connecting said fluid cooled tubes into said fluid circulation system.

4. A fluid heating unit having a fluid circulation system and comprising upwardly extending walls including upwardly extending fluid cooled tubes defining a secondary furnace chamber, a plurality of cyclone furnaces each having a substantially cylindrical combustion chamber defined in part by a circumferential wall, each combustion chamber having the major portion of its axial length extending into said secondary furnace chamber, with substantially the entire length of at least a portion of the circumferential wall of each combustion chamber being formed by an intermediate portion of one of the outer boundary walls of said secondary furnace chamber and a portion of some of the fluid cooled tubes thereof, a gas outlet in an end wall of each combustion chamber opening to said secondary furnace chamber, means including combustion chamber fuel and air inlets disposed exteriorly of said secondary furnace chamber for introducing a combustible mixture into each combustion chamber for discharge through its respective gas outlet into said secondary furnace chamber, said secondary furnace chamber including an upwardly extending Wall disposed opposite and close to said gas outlets and arranged to direct the gases discharging from each combustion chamber over and into heat transfer relation with a portion of the outer surface of the circumferential Wall of each combustion chamber, whereby a part of the fluid cooled tubes of each circumferential Wall absorb heat concurrently from the hot gases therein and from the gases flowing through said secondary furnace chamber, and means connecting said fluid cooled tubes into said fluid circulation system.

5. A fluid heating unit having a fluid circulation system and comprising upwardly extending walls including upwardly extending fluid cooled tubes defining a secondary furnace chamber, a pair of cyclone furnaces arranged in one wall of said secondary furnace chamber at substantially the same elevation, each cyclone furnace having a substantially cylindrical combustion chamber arranged with its axis substantially horizontal and defined by circumferential and end walls including intermediate portions of some of the fluid cooled tubes of said secondary furnace chamber, each combustion chamber having the major portion of its axial length extending into said secondary furnace chamber substantially perpendicular to said one wall of said secondary furnace chamber, with substantially the entire length of at least a portion of the circumferential wall of each combustion chamber being formed by one of the outer boundary walls of said secondary furnace chamber, a gas outlet in one of said end walls of each combustion chamber opening to said secondary furnace chamber, means including combustion chamber fuel and air inlets disposed exteriorly of said secondary furnace chamber for introducing a combustible mixture into each combustion chamber for discharge through its respective gas outlet into said secondary furnace chamber, said secondary furnace chamber including an upwardly extending wall disposed opposite and close to said gas outlets and arranged to direct the gases discharging from each combustion chamber over and into heat transfer relation with a portion of the outer surface of the circumferential Wall of each combustion chamber, whereby a part of the fluid cooled tubes of each combustion chamber absorb heat concurrently from the hot gases therein and from the gases flowing through said secondary furnace chamber, and means connecting said fluid cooled tubes into said fluid circulation system.

6. A fluid heating unit having a fluid circulation system and comprising upwardly extending walls including upwardly extending fluid cooled tubes defining a secondary furnace chamber, circumferential and end walls including intermediate portions of some of the fluid cooled tubes of said secondary furnace chamber defining a combustion chamber of substantially circular cross-section arranged with its major axis substantially horizontal and having the major portion of its axial length extending into said secondary furnace chamber, with substantially the entire length of at least a portion of said circumferential wall being formed by one of the outer boundary walls of said secondary furnace chamber, means including combustion chamber fuel and air inlets disposed exteriorly of said secondary furnace chamber for burning a slag-forming solid fuel in said combustion chamber under a mean combustion chamber temperature above the fuel ash fusion temperature, means forming a gas outlet in one of said end walls of said combustion chamber opening to said secondary furnace chamber for the discharge of heating gases carrying slag particles in suspension into said secondary furnace chamber, said secondary furnace chamber including an upright outer wall opposite and close to said gas outlet arranged to receive the impact of the slag particles in suspension in the gases discharged from said combustion chamber and to direct the gases over and into heat transfer relation with a portion of the outer surface of the circumferential wall of said combustion chamber, whereby a part of the fluid cooled tubes of said circumferential wall absorb heat concurrently from the hot gases therein and from the gases flowing through said secondary furnace chamber, a slag outlet in the lower portion of the References Cited in the file of this patent FOREIGN PATENTS 512,102 Belgium June 30, 1952 360,251 Great Britain Nov. 5, 1931 706,321 Great Britain Mar. 31, 1954 n turret; 

